slant 6 starter

Hello I have a slant 6 motor and well my starter was going so i replaced it with a rebuilt starter with lifetime warranty. Anyway. I installed the new starter. The old one had a fitting between the transmission and starter. So I left that in and installed the new starter. Now the car starts faster but it make a grinding sound after the starter is engaged. At first it sounds normal when the key is turned no grinding but when the starter winds down it make grinding sound. When the engine starts sounds like the starter grinds while it slowing down. I dont think stuck to the fly if the engine is running?
My friend think i should try removing that what he called the spacer because it did int come with the new starter.

Thanks Casey